Curing (hereafter, it may be abbreviated as photo-curing) by a polymerization initiator (hereafter, it may be abbreviated as a photo-polymerization initiator) sensitive to active energy ray, such as, for example, infrared rays, visible rays, ultraviolet rays, X-rays, has many advantages, such that it is possible to cure at lower temperature and in a shorter period of time, and to form finer patterns, etc., as compared with curing (hereafter, it may be abbreviated as heat-curing) by a heat sensitive polymerization initiator (hereafter, it may be abbreviated as a thermal-polymerization initiator), therefore, these photo-polymerization initiators have been used, as photo-curing materials, widely in the fields of surface processing of a paint, a printing ink, a dental material, a resist, etc.
The photo-polymerization initiators to be used in photo-curing technology are largely classified into three groups of photo-radical generators, a photo-cation (acid) generator and a photo-anion (base) generator, depending on the active species generated. The photo-radical generator is a photo-polymerization initiator for generating radical species by irradiation of the active energy ray, and it is the generator which has been used widely in the past, however, it has the drawbacks that the radical species are deactivated by oxygen in air, a polymerization reaction is inhibited and curing is suppressed. Therefore, in using the photo-radical generator, special contrivance has been required, such that oxygen in air is intercepted. The photo-cation (acid) generator is a photo-polymerization initiator, which generates an acid by irradiation of active energy ray and thus does not receive inhibition by oxygen, therefore various kinds of the photo-cation (acid) generators have been provided to practical use since the latter half of 1990's. However, there may be the case where the acid generated by irradiation of the active energy ray remains in a system even after curing, and there have been pointed out a problem of decrease in film performance, caused by denaturation of a cured film after curing of a photo-sensitive composition containing the photo-cation (acid) generator, or a problem of corrosive property to a metal wiring on a semiconductor substrate, caused by the acid. In contrast, the photo-anion (base) generator is the generator which generates a base by irradiation of active energy ray, and thus does not receive inhibition by oxygen in air, and a problem of corrosive property or denaturation of a cured film hardly occurs, therefore research and development thereof has been actively carried out in recent years.
Recently, there has been investigated a means for applying the photo-sensitive composition containing the photo-anion (base) generator to a photo-resist material or a photo-curing material, etc. For example, there has been proposed a method in which amines are generated in an epoxy resin by irradiation of active energy ray, and subsequently the epoxy resin is cured by heating treatment, by utilizing that, for example, a compound having an epoxy group cures by generating a cross-linking reaction by an action of a base (for example, NON PATENT LITERATURE 1).
In the case of curing an epoxy-based compound by amines generating from the photo-anion (base) generator, a primary amine or a secondary amine requires a long period of time for a cross-linking reaction with an epoxy group, therefore, it is necessary to carry out heating treatment, etc. at high temperature, in order to increase cure rate. In addition, it is also possible to increase cure rate by increasing a crosslinking density with using a polyfunctionalized primary amine or secondary amine, however, it is necessary for all amines to be made photo-latent (protected), and solubility is likely to be reduced significantly. In contrast, when the epoxy-based compound is cured by amines, such as a tertiary amine, amidine, guanidine, phosphazene, these amines easily function as a catalyst, and thus can cure the epoxy-based compound, even by using relatively less amount, and particularly in combined use with a cross-linking agent (for example, polyfunctional carboxylic acid, polyfunctional phenol, polyfunctional thiol, polyfunctional β-ketoester, etc.) having an acidic proton, it can cure the epoxy-based compound at low temperature and quickly.
As such amines, there have been known conventionally a photo-anion (base) generator, such as, for example, a tertiary amine, an amine-imide-based compound (for example, PATENT LITERATURE 1) which generate amidine, such as 1,5-diazabicyclo[4.3.0]-5-nonene (DBN), 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) by irradiation of active energy rays, and an ammonium borate-based compound (for example, NON PATENT LITERATURE 2). In addition, there have been known a photo-anion (base) generator, such as a tetraphenyl borate-based compound (for example, NON PATENT LITERATURE 3) which generates a strong base, such as guanidine, such as 1,1,3,3-tetramethylguanidine (TMG), 1,5,7-triazabicyclo[4.4.0]deca-5-ene (TBD), 7-methyl-1,5,7-triazabicyclo[4.4.0]deca-5-ene (MTBD), or phosphazene, for example, by irradiation of active energy rays; a compound (for example, PATENT LITERATURE 2) comprising a carboxylic acid, which is decarboxylated by irradiation of active energy rays, and amines; a benzoic acid-based compound (for example, PATENT LITERATURE 3) forming a cyclic ester by irradiation of active energy rays. On the other hand, as a strong organic base exceeding amidine or guanidine, biguanides have been known (for example, PATENT LITERATURE 4, NON PATENT LITERATURE 4, NON PATENT LITERATURE 5), and an example where the biguanides are used for epoxy curing application has also been reported (for example, PATENT LITERATURE 5). In addition, such an application example has been known as a potential heat-curing catalyst by formation of a salt between a thermally decomposable compound and biguanides, although it is not as the photo-anion (base) generator (for example, PATENT LITERATURE 6, PATENT LITERATURE 7).